Plasmonic antennas and meta-screen for alleviating the trade-offs in near-field optics

Yan Wang

The Edward S. Rogers Sr. Department of Electrical and Computer Engineering (Electromagnetics)

Abstract:

Focusing optical waves with sub-wavelength resolution enables many disciplines such as nearfield microscopy, spatially resolved spectroscopy and photolithography. Sub-wavelength focusing is commonly achieved by transmitting light through single sub-wavelength apertures, which are ususally on the order of a few tens of nanometers in size to achieve the desired spot size. In this size regime, the scheme entails a trade-off between the resolution, which is represented by the spot size, and the attenuation imposed by the aperture on the optical field. Overcoming this trade-off can enhance numerous applications and in particular those which rely on an intense field.

We present a "meta-screen", a metallic sheet patterned with an array of nano-sized slot antennas, for the purpose of near-field sub-diffraction focusing. The arrary of slots separated by subwavelength distance sharpens the transmitted beam through near-field interference. This design topology stems from the sub-diffraction analysis at microwave frequencies, as well as recent developments in plasmonic nano-antennas. Important issues such as the operating principle of the meta-screen, the characteristics of plasmonic slot antennas, the impact of the array element number, and the effect of asymmetry due to the presence of a supporting substrate are discussed.

Biography:

Yan Wang received a B.ASc. and a M.ASc degree from the University of Toronto in Electrical Engineering. During her Master's thesis research, she worked with professor Eleftheriades on plasmonic couplers for nano-optics applications.  She is currently working on her PhD degree with both professor Eleftheriades from the Electromagnetics group and professor Helmy from the Photonics group. The areas of her research include plasmonic antennas and arrays, and near-field nano-sized focusing for sensing and lithography applications.